A pick of this type is disclosed in DE 37 01 905 C1. In this case, the fastening sleeve is realized as a clamping sleeve which is formed from a resilient elastic material, for example, sheet steel. It comprises a longitudinal slot which is delimited by sleeve edges. The fastening sleeve diameter is able to be varied by means of the longitudinal slot, it being possible to move the sleeve edges toward one another (small diameter) or are they are spaced further from one another (large sleeve diameter). Different clamping states can be achieved in this way. The support element which is realized as an anti-wear disk is pulled onto the fastening sleeve. The support element comprises a circular cross section and is penetrated by a bore. In this case, the bore is dimensioned such that the fastening sleeve is held in a pre-clamping state with a reduced outside diameter compared to its relaxed state. The outside diameter generated in this manner is chosen in such a manner that the clamping sleeve is able to be slid into a pick receiving means of a pick holder with a small amount or no expenditure of force. The insertion movement is delimited by means of the support element. As the pick shaft is inserted further into the bore, the support element is moved into a region of the pick shaft that is not encompassed by the clamping sleeve. The fastening sleeve then springs open radially and is clamped in the bore of the pick holder. In this way the round shaft pick is held so as to be axially captive, but freely rotatable in the circumferential direction. To dismantle the pick, it is driven out of the pick receiving means by means of a mandrel which acts upon the back of the pick shaft.
EP 1 427 913 B1 discloses a disk for a rotatable cutting bit having: a front side and a rear side, the front side having several ribs and the rear side having several recesses. The rear side further comprises a beveled edge which is arranged circumferentially with respect to a central bore. The recesses are spaced uniformly from one another and from the beveled edge. The beveled edge is angled sharply into the surface of the rear side. The sharp angle can result in the disk not resting flatly on the holding block arranged below it, which leads to increased abrasion of the disk and of the holding block. In addition, the sharp transition can result in the disk becoming jammed and its rotation prevented, as a result of which one-sided wear is produced on the cutting bit.
EP 2 639 402 A2 consequently proposes a bit, in particular, a round shaft bit, having a bit head and a bit shaft, a fastening sleeve being held in the region of the bit shaft, and having a support element which comprises a guide region, the support element comprising a protruding centering attachment on its bottom surface. The centering attachment comprises a centering surface, which extends at an angle to the center longitudinal axis of the bit and merges into a circumferential support surface, which extends radially to the center longitudinal axis by means of a set-back recess. The recess, in this case, is worked into the centering surface and the support surface such that in the mounted state it receives an oppositely situated sharp edge of the bit holder. The support element accordingly, within the framework of the production tolerances, does not rest on the edge of the bit holder, as a result of which a flat supporting of the support element on the provided support surface of the bit holder is ensured. As a result, the abrasion of the support element and of the bit holder is reduced and at the same time the free rotation of the disk is improved. However, there is an edge in the transition from the centering surface to the recess. The edge provides a continuity jump with a negative effect on the rotation and consequently on wear behavior. In addition, as a result of the recess molded both in the support surface and in the centering surface, waste material is able to pass into the region of the bit shaft and obstruct the rotation of the bit there and increase the amount of wear. A further disadvantage is produced by the fact that as a result of the recess, the support surface between the centering surface of the support element and the corresponding surface of the centering receiving means of the bit holder is made smaller, as a result of which the surface pressure on the remaining surface increases under the same load. This also leads to increased wear in the region with the support element at the same time being guided less at the side.